The correct process for doing this is to find the bmdb (battle_models.modeldb) entry name in the "from" mod's descr_strat or campaign_script (depending on whether the character starts on the map or is spawned), search this entry in the "from" mod's bmdb file, and then find all the referenced models, textures, and sprites. You can actually copy over the entire bmdb entry and delete the old one and old assets in the "to" mod. This requires that you to know how to read bmdb.
My guess as to why the model is completely black is that it's using the wrong textures. The game is finding assets with the names specified in bmdb (otherwise it would CTD from the battle map), and these textures are set up for the correct faction (or the model would be a silver surfer), but the textures are incorrect for the model.